Yeah true, though as an open world fantasy game maybe they feel they have a spot, especially since there's no Elder Scrolls to compete with, and The Witcher has been pushed into next year.
I think so yes, but I don't hold Drew up on a pedestal either, nor feel Walters is totally useless. As far as I'm aware he wrote both Garrus and Wrex in Mass Effect, along with Garrus' story arc in Mass Effect 2. I don't think he's a bad writer so much as maybe a weak lead writer, as both ME2 and ME3 have the most fragmented main narratives (ME2 especially). But it's really impossible to tell without knowing who exactly wrote what. People kept attributing Cerberus rise into a super group in ME2 to Walters, but then I heard that was Drew's doing, so *shrug*.
That being said, I feel the MacGuffin is both their fault, because I maintain that they wrote themselves into a corner with the first game. I've said this since before Mass Effect 2 came out: ending the first game on "we stopped the Reapers, but...the Reapers!" was doomed to cause problems and make the first game inconsequential. The wrote a mysterious, unfathomably powerful nemesis desperately fighting for its return for the return of its kind after almost being beaten by the previous cycle, then defeated, only to then in the same breath say there's more and they're coming so we have to beat them too. I've always felt Mass Effect was written under the the possibility there wouldn't be any more games regardless of intentions, but they had to leave room for a sequel. So we got the Reapers returning in all their might, and suddenly BioWare is faced with the problem of how to believably get rid of them.
The MacGuffin was dumb but I feel they in many ways doomed themselves once the credits rolled in Mass Effect 1.